1. Field of Invention
This invention relates to improvements in a brake system and in particular to a brake wear indicator useful in a vehicle pneumatic brake system.
2. Brief Statement of the Prior Art
The brakes which are commonly used on vehicles, particularly trucks and trailers, are air pressure actuated. These commonly have a brake actuator which comprises an air pressure chamber and flexible diaphragm that is mechanically linked to the brake by a push rod or other mechanical linkage having a travel which increases as the brake member, such as a brake pad or brake lining, wears during use. In the typical pneumatic brakes on trucks and trailers, the actuator is visible and the common practice for determining the magnitude of the wear is to observe the degree of travel of the actuator rod. This can be accomplished by marking the rod in its most retracted position within the actuator (brakes off), having a companion apply the brakes, and measuring the length of the push rod extension. Alternatively, one can forcibly extend the actuator against the bias of the return spring of the actuator assembly. Most vehicle codes provide a safe or permissible limit to the magnitude of travel of the actuator rod which commonly is from one to about two inches.
The current brake systems are, accordingly, difficult to inspect and require a companion or special equipment for determining the degree of travel of the brake actuator push rod. This inspection is made by vehicle operators, mechanics and inspection officials, however, it is not made as routinely or frequently as should be, owing to the difficulty of such inspection, ultimately presenting a significant potential for hazardous condition of vehicles.